Transformer system



Dec. 16, 1930. H. WHITTLE VTRANSFORMER SYSTEM Fi1ed.Aug. 27, 1927 y. M M

Patented Dec. 16, 1930 UNITED STATES Alnaralwr oFFics HORACE WHITTLE, OF MAPLEWOOID', NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATON OF NEV YORK j TRANSFORMER SYSTEM Application filed August 27, 1927, Serial No. 215,863.` Renewed June 6, 1930.

This invention relates to electric wave transmission, and particularly to transformer circuits.

An object of the invention is to vcontrol '5 phase shifts or phase relations of waves, es-

pecially of complex waves, for example for reducing deleterious effects of waves interferingv with signaling, or' for increasing directional selectivity of radio antenna systems. One specific aspect of the invention is a wave antenna circuit for receiving radio tele phone signals from a given direction without undue disturbance from waves incident on the antenna from other directions. To balance out or neutralize the interference c0mponent in current having components due to signal energy and interfering energy re-. ceived by the antenna, an interferencecompensating current derived from interfering energy received by the antenna is combined with the first current in phase Vopposition to its interfeience component. The two currents travel paths which differ as regards the transformers included in the two paths. In accordance with the invention, the relative phase shifts produced in the tw-o paths by the transformers are properly adjusted; for otherwise there would result a relative phase shift in the interference current component Scand the compensating interfering current,

and this relative shift would vary with frequency in such a manner that it could not be adequately compensated for, over the requisite frequency range, by adjustable phase shifting devices such as are customarily employed'to adjust the phase relation of two single frequency currents. Y

If desired, the relative phase shift that over the frequency rangeof the signalssodesired phase relations, is extended to a system including a plurality of antennae.

The general character of the system will now be indicated somewhat more specifically. The system includes three wave antennae, each of a general type disclosed for example in- Kellogg Patent 1,487,339, March 18, 1924. f Each wave antenna comprises two parallel -wires extending in the direction from which circuit leading to the input circuit for the radio receiver. l j A VThe' secondary winding of the' reection transformer is connected between the antenna wires. The primarywinding is connected from the midpoint of the secondary winding to earth. Y r f llaves that approach the antenna from the direction from which it is desired to re# ceive signals cause longitudinal currents to ow in the antenna toward the reflection transformer. These longitudinal currents pass from the antenna wires through the two halves of the secondary winding of the transformer to the midpoint ofthe winding, in such directions as to produce magnetic fields, which neutralize each other, and these currents flow from the midpoint of the second- Vary winding through the primaryrwinding to earth. 'Il his current flow in the primary winding induces a voltage in the secondary winding which causes current to circulate in the loop formed by the secondary winding, the antenna wires andthe primary winding of the signal transformer. rThis current flow in the primary windingof the signal transformer induces a voltage in the secondary winding, which causes current to fioivin the circuit connecting the secondary winding 'to the radio receiver. The primary winding of the compensating transformer receives very little of the longitudinal current flowing in the antenna Wires due to waves from the direction of approach of the desired signals.

Vaves that approach the antenna from the direction opposite that from which it is desired to receive signals, produce longitudinal antenna currents which pass through the two halves of the primary winding of the signal transformer in such directions as to produce magnetic fields which neutralize each other and induce no signal voltage in t-he secondary winding. Very little of these longitudinal currents flows through the primary winding of the reflection transformer, and consequently they have little tendency to cause interference currents to be received in the radio receiver.

Compensation is especially desirable for deleterious effects of waves that approach the antenna from directions other than the direction of the length of the antenna. For example, waves approaching at an angle of, say, 45 degrees to the direction of the desired waves may induce voltage in the antenna that result in a considerable current flowing through the primary winding of the reflection transformer. To compensate for the deleterious effects which this current tends to cause in the receiver, use is made of'tli, current flowing through the primary winding of the compensation transformer, as a result of voltage induced in the antenna by these waves.

Interference waves reaching the radio receiver due to voltages applied to the primary winding of the reflection transformer suffer phase shift due to transformation .in that transformer and further phase shift due to transformation in the signal transformer- Interference waves reaching the radio receiver due to voltages applied to the primary winding of the compensation trans` formei suer phase shift due to transformation in that transformer. In accordance with the invention this phase shift is made substantially equal to the sum of the phase shifts in the reflection transformer and the signal transformer, over a frequency range including the frequencies of thehwave coniponents of different frequencies in the coniplex signal wave or waves to be received. dien this equality of phase shifts obtains, the interfering waves from the secondary winding of the compensating transformer can be balanced against the interfering waves from the secondary winding of the signal transformer, to reduce t-he interference and increase the ratio of signal power 'to interference power in the radio receiver output. In order that the phase shift required for the compensating transformer may be sufficiently small to avoid undue difficulty in practical construction of the transformer,

the phase shift in each of the other two transformers is preferably made as small as is readily practicable.

In some cases the phase shift in the compensating transformer may differ from the sum of the combined phase shifts in the other two transformers in a desired manner over the frequency range of the signal coinponents of the complex wave oi waves to he received, and the difference be compensated for by phase shifting means. For example, the difference may be proportional to frequency, over the range mentioned, and may be compensated for by an adjustable phase shift network of the type known as a phase rotator, which is capable of producing phase shift proportional to frequency.

The three wave antenna are spaced apart a certain fraction of the wave length of the desired signals, in the direction perpendicular to the lengths of the antenna, and constitute an antenna array of the general form well ,known as a broadside wave antenna system.

The circuits connecting the secondary windings of the signal transformers and the secondary windings of the compensating transformers to the input circuit of the radio receiver include bridge transformer networks, which have sometimes been termed hybrid coils, for combining the outputs from the signal transformers and combining' the outputs of the compensating transformers and balancing this second combined output against the interference present in the first, to prevent the interference from reaching the receiver. Y

Each of the bridge transformer networks comprises two three-winding transformers. In accordance with the invention, the phase shifts in the two transformers of any given bridge transformer network may be equal, over the frequency band comprised in the signals to be received, so that proper phase relations between the waves transmitted through the transformers are preserve-d, as pointed out hereinafter.

Two two-winding transformers are connected respectively in two of the circuits connecting the antenna output transformers to the input circuit of the receiver. They introduce phase shifts equal respectively to those in two of the bridge transformer networks neither of which is included in either of these two connecting circuits but one or the other of which is included in each of the others of the connecting circuit; or the two-winding transformers mav introduce respective phase shifts which differ in a desired manner from phase shifts in the two transformer bridge networks, over the frcquency band comprised in the signals to be received, and the differences be then compensated for by phase shifting devices. For ei;- ample, t-he differences may be proportional to frequency, and the compensations' for the differences be effected by phase rotators.

In accordance with the invention, a transformer that introduces a phaseshift which balances a phase shift in one or more other transformers as described above, may have its impedance ratio different from that of one or more of the other transformers, or may have the impedance of its primary or secondary winding, Vor each, different from that of one or more of the other transformers.

Other objects and aspects of the invention will be-apparent from the'followingdescription and claims.

Fig. 1 of the drawing isa circuit diagram of the system described above; and Fig. 2 represents a bridge transformer network of a type employed in the system of Fig. 1.

A wave antenna A has a reiiection transformer 1, a signal transformer 2, and a compensating transformer 3. Wave antenna B has reflection, signal and compensating transformers 4,5, and 6 respectively. Vave antenna C has reiiection, signal and compensating transformers 7, 8 and 9. Each antenna extends from its reflection transformer toward the direction from which desired signals approach. The desired signals may be, for example, radio telephone signals. The antenna are spaced apart a certain fraction of the wave length of the desired signals, in the direction perpendicular to the lengths of the antennae, and Vform a broadside wave antenna system.

The secondary windings of transformers 2, 3, 5, 6,8 and 9 are connected to the primary windings of sectionalizing transformers 10, 11, 12, 13, 14 and 15, respectively. The secondary windings of these `sectionalizing transformers are connecte-d respectively to the input windings of three-winding transformers 16, 18, 21, 22, 17 and 19.

Transformers 16 and 17 form a bridge transformer network B-31 which combines the signals from transformers 2 and 8 and transmits the combined signals to the input winding of a three-windingv transformer 2O.V

Transformers 20 and 21 form a bridge transformer network B-33 which combines the signals from transformers 2 and 8 with those from transformer 5 and transmits the coinbined signals to the input winding of a threewinding transformer 24.

Transformers 18 and 19 form a bridge transformer network B-32 which combines the compensating currents from transformers 3 and 9 and transmits the combined compensatin g currents to the input winding of a three-winding transformer 23. Transformers 23 and 22 form a bridge transformer network ]3-34 which combines the compensating currents from transformers 3 and 9 with those fromV transformer 6 and transmits the combined compensating currents to the input `winding of a three-winding transformer 25.

Transformers 25 and 24 form a bridge transformer network B- which balances thefcompensating currents from coils 3, 6 and 9 against the signal currents from coils l2, 5 an-d 8, to reduce or eliminate interference in the signal currents before the signal currents reach radio receiver 40. The radio receiver may include means for deinodulating or detecting carrier waves modulated by speech or other signal waves, and a telephone receiver or other signal indicator.

The bridge transformer networks lf3-81' to B-35 havev associated tlierewitlibalancing networks N-31`to N-S respectively, for balancing the impedances of the output circuits of'the bridge transformer networks.

The transformer bridge networks may ail be alike. The bridge transformer network B-S is shown in Fig. 2. Each of the transformers 24 and 25 has, upon its core, three.

windings each wound in a definite direction. The input winding `W1 of transformer 24 is connected to the inputAY circuit 24 leading Y exists between thebalancing network N and the receiving circuit 41. The transformer arrangement or Vbridge transformer network constitutes a combining circuit which Vis adapted to combine currents flowing from 'bridge transformer networks B-33 and B*34 for transmission to the radio receiver 40.

The manner in which a bridge transformer network such as 13-35 functions may be ei:- plained as follows. Let it be assumed that energy is to be transmitted from circuits 24 and 25 into coil Irl- 35, and that energy is to be transmitted from network Bhf to the output or receiving circuit 40. ficcordiiigly.I the flow of currents in the windings W1 and W2 of transformers 24 and 25 may be assumed to be in the relative directions indicated by the'arrows adjacent thereto. These currents in windings H and im will induce electromotive forces in windings W3 and .75 and W4. and W76, respectively, which will tend to cause the flow of currents therethrough. The windings 73 and Vi are so arranged that the flow of currents therethrough due to the currents iii circuits C1 and C2 as indicated, will aid each other, whereas windings W5 and WVG are differently arranged so that the flow of currents therethrough will oppose each other under the same circun'istances. rlie arrows adjacent to these windings represent the polarity ofthe electromotive forces across "hese `windings, under the given circumstances. lf the currents flowing in circuits 2a and 25 are of equal amplitudes and of the same phase, cqu al voltages will be induced in windings W5 and WG which are oppositely directed so that there is no resultant effect in the circuit of the network N-35. Under the same conditions, the circuit 40 will receive all the energy from the circuits 2li and 25. lf, however, the current flowing in the circuit Q-l is greater or less than the current flowing in the circuit 25, then the magnitudes of the potentials iminessed across the windings T5 and XVC, will be unequal, and current will flow through the balancing network ll-35 of an amount propm'tional to the difference between the potentials impressed across these windings.

lf the currents flowing in circuits 24; and 25 be of equal amplitudes but of opposite phases, the potentials set up across the terminals of windings Vila and XY, will be of equal magnitudes, but these currents will be substantially neutralized by virtue of their presence in the output or receiving circuit llO in phase opposition. ln this case the entire energy from circuits 2e! and 25 will be dissipated in the network ll-B. 'if his property of the bridge transformer network made use of when uncesired signal or interference currents are combined in phase opposition, as is the case in the bridge transformer network B-B in the system of Fig. l. Furthermore, with the impedance of the network nl-35 substantially equal to that presented by the receiving circuit 40', currents flowing in circuit 24: will not be transmit-ted to circuit 25', and vice versa. Therefore there is no interaction between circuits Ql and Q5.

lt is desired that in the case of each of the bridge transformer networks l-Sl to the two inputs to the network be in phase and be equal in magnitude,` so that the waves from transforn'iers 2 and 8 will be added cumulatively in network l--3l and will be augmented by the waves from transformer 5 in network Bllf, and so that the waves from compensating transformers 3, and E) will similarly be Vcumulatively added by networks lli-l2 and B Further. it desired that the input to transformer 25 be equal in ma nitude and opposite in phase to the interference component of the input to transformer 2. so that by the network B-fl the combined compei'isating waves will be opposed to the interference component of the combined waves from transformers 2, 5 and 8 to reduce or eliminate that component, with the result that the signal component alone will be transrn itted to the radio receiver Ll0.

For interference waves from any given direction other than the direction from which the desired waves approach, the desired equalities in magnitudes are obtained with the aid of attenuators, for example, artificial lines Alf-51, [iL-52 and ELL- 55, which may be adjustable, rllhe attenuator AL-l renders the input to transformer E20 equal in magnitude to the input to transformer 21. rEhe attenuator Afr-52 renders the input to transformer 23 eeual in magnitude to the input to transformer 22. The attenuator AL- is adjusted to render the input to transformer 25 equal in magnitude to the interference component of the input to transformer 2li, for interference waves from any given direction other than the direction from which the desired waves approach.

Phase-Shifters 13S- 61, PS62 and ES-G5 assist in obtainingr the desired phase relations. The transformers 2, 3, 8 and 9 are farther' than the transforn'iers 5 and 6 from the apparatus comprising the transers l0 to Each of the circuits 2, 3', o and 9 which connect transformers 2, 3, 8 and 9 to transformers l0, ll, 14 and l( respectively is of the same length, but is longer than each of the circuits 5 and 6 which connect transformers 5 and 6 to transformers l2 and 13 respectively and which are of the same length. The phase-shifter PS3-6l compensates over the frequency range of the desired signals, for the difference between the phase shift produced by line 2 or 8 with artificial line AL-l, on the one hand, and line 5 on the other hand. The phase-shifter PS-62 similarly compensates for the difference between the phase shift produced by line 8 or 9 and artificial line Alli- 52, on the one hand, and line 6 on the other hand. A transformer 26 produces in waves to `be delivered t0 transfornier 21 a phase shift equal, over the frequency range vof the desired signals, to the phase shift produced by bridge transformer network B-3l in the Waves to be delivered to transformer 20. A transformer 27 similarly compensates for the phase shifts in network Bw. For interference waves from any given direction other than the direction from which the desired waves approach, the phase shifter 13S-65 is adjusted to compensate, over the frequency range of the desired signals, for the difference between the phase shifts which the antennae lines produce in the interference waves that the antennae transmit to the lines 2', 5 and 8', on the one hand, and the phase shifts which the antennae lines and the adjustable attenuator Alf-55 produce in the interference waves that the antennae transmit to lines 3', 6 and 9', on the other hand.

The transformers included in the circuit are so constructed that the phase shifts which they produce over the frequency range of the desired signal waves are such as peramy mit thedesired phase relations to be ob` tained. Transformers produce. phase shifts so varying with frequency that .in cases in which the rangefof signal `frequencies is considerable, for instance in the case of a speech side hand, adjustable phase shiftcrs such as Pfl- 61, PS1- 62 and PS- are incapable of adequately compensating for the `phase shifts of the individual transformers.V

Mcreover, in systems such as that of Fig. 1

`it is desirable to employ in transmission but transmits `compensating interference waves to the compensating circuit 3 through onlythe transformer 3.1 The phase shiftsf which the dilferentnumbers of transformers channels which should have equal overall phase shifts, different numbers of tandem connected transformers.. For example, antenna A transmits interference Vwaves to line 2 through transformers 1 and 2 in tandem,

introduce inlthe channels which` should have equal overall phase shifts can not be made equal by constructing the transforme'rsalike, as they might. be Vwere the numbers not different; and moreover, it is sometimes de- Vsirable that the transformers in one Vof the channels, as for example the transformer 3',

differ from those in another of the channels, as for example, the transformers 1 and 2, with resp-ect to electrical characteristics such as `impedance ratio or .the impedance Vof one or mo-re windings, for instance.. Further,in

systems such Vas that of Fig. 1, itis desirable to employ .in transmission channels .1'. which should have equal overall phase shifts,

or phase shifts which differ proportional-ly from, the phase shifts produced by the threewinding transformers 16 and 17. f

.To obtain the desired phase relations in the system of Fig. 1,A over the frequency rangefof the desiredsignals the following conditions as to relative phase.v shifts `in thef I; transformers aresatisfied:.Thephase shift- Ain"transformer 3j is equal to the sum of the phase shifts intransformers -1 and" 2;( the shift intransformer 6 is'equal .tojthe `sum ofthe'shifts. in transformers tandlj; the

theshifts in Vtransformers. `3, Gand-9 lare equal; the shifts in transformers 10, 12 and 14 are equal;the shifts intransformers 11,l

if shift vin transformer 9 is equal `to, the sum ofthe shifts in ftransformers'( and ,8; Athe shifts in transformers 1, llv and A7 areequa-l;

the shifts in transformers2, and'Sare equal;

13 and 15 are equal; the shifts intransformers 16 and 17 are equal; theV shifts in trans-1 `ff'rrmers 18 vand 19 are .equalgthe'shifts 'in' transformers@ and21 areequal; the shifts 1 in transformers22and 23 are equal; the shifts Vin transformers 24a-nd25 are equal;

the shifts in transformer 26 is equal to the transformers 22'and 23. -For disclosure of a manner in which the transformersmay be constructed to give the requisite phaseshifts,

and 21 is equalto :the shiftproducedfby reference. is `made to Patent No.,1,759,332,

issuedrMay 20, 1930, on the copending appl1. cationV of Horace Whittleand D. G. :Grimley, Serial No. 177,518 filed March 23,1927. Of course the phase equalities expressed above are notzeXact as obtained inA practice, butI are substantial equalities. .AsV an eX- ainple ofthe` closeness of approach to the absolute or: exact equalities, which, in practice, may be made by constructing the transformers in.' accordance with the, teaching of the` application just mentioned, it `may, be stated that transformersvhave been constructedj in which the phase equalities. expressed above obtained to within less than v minutes of phase angle over any 5000 cycle band of frequencies between 45V and 65 kilocycles. Y

Under theseconditions of equality of phase shift, when the adjustable phase Shifters in the system of Fig. 1 are set tojbalanceoutY an unwanted signaler unwanted signals, s the .balance will hold over a frequency range of at least 5000 cycles.Y l r In orderto avoid any necessity forgiving the compensating transformers, such as 8, 6 or 9, aphase shift so large V that it would be unduly'diflicult toobtain in each of those transformers, the transformers 1, 2, ft, 5, g 7 and 8 may each be made to have as small a phase shiftv as practicable, V`over the frequency range of the ,desired signals.

`ln `the system Yof Fig..1 instead of having i the Vphase shift of transformer 3 balance the phase'shift of'transformersl and 2,=it may i differ from them in a desired mannerover vthe frequency-range of the signals to be received, andthe difference be compensated for by phase shifting means. For example, the difference vbetween the phase shift of transformers?. and that of transformersl and 2V may be madesubstantiallyproportional tofr'equencyoverthe frequency range of the desired signals andthen'may be'cornpensatedfor 'by theadjustable phaseshifter PS`65, which iscapable of Vcompensating formers 5 and 8v like transformer 2, and the transformers' and 9 like ,the transformer 3, so that the compensationintroduced by phase shifter l?S--65 for` `the transfartners 1,; and

3 will be properly applicable to the transformers a to 9 also.

Similarly, the adjustable phase shift-ers PS-fl and PS-G2 can be utilized to conipensate for differences between the phase shift in transformer QG and the phase shift -in network B-tl, and between the phase -times desirable to employ such factors as inductances, capacity and resistance as effectively parts of the transformer construction although external to the core and windings. For example, vit is sometimes desirable to employ series iiiductance or series capacity or shunt reactance which may be variable. rl`he eipression transformer as used in this specification and in the claims may include a transformer having such auxiliary impedances effectively portions thereof, as well as'fa transformer not dependent on such eX- ternal impedances for its desired shunt and series impedances.

lVhat is claimed is:

1. In combinatioina circuit, one or more transformers in said circuit, and one or more other transformers so connected to said circuit and producing,r in waves transmitted therethrough phase shifts of such magnitude relative to the phase shifts produced by the Vfirst mentioned transformers in waves in said cicuit as to compensate for the latter iliase shifts, one of said first mentioned transformers having` electrical constants substantially different from those of any one of said other transformers. i

Q. In combination, a circuit, one or mor transformers in said circuit, and one or more other transformers so connected to said circuit and pioducingi nwaves transmitted therethrough phase shifts of such magnitude relative to the phase shifts produced by the first mentioned transformers in waves in said circuit as to compensa te for the latter phase shifts, said first mentioned transformers diftering` in'nuinbcr from said other transformers.

3. In combination, a circuit, one or more transformers in said circuit, means for supplyiiig, waves of a given range of frequencies to said circuit, and adjustable phase shift Amea-ns and one or more other tansformers,

said means and said other transform-ers being so associated with said circuit and having' such frequency-phase shift characteristics relative to those of the first mentioned trans-y foriners as to compensate for phase shift,

nels,

ers having electrical constants substantially different from those of any one of said other transformers.

4. In combination, a circuit, one or more transformers in said circuit, means for supplying waves of a given range of frequencies to said circuit, and adjustable phase shift means and one or more other transformers, Said means and said other transformers being` so associated with said circuit and havingsuch frequency-phase shift characteristics relative to those of the first mentioned transformers as to compensate for phase shift, over said frequency range, produced by said first mentioned transformers in waves in said circuit, said first mentioned transformers di ffering in number from said other transformers.

5. In combination, two wave transmission channels, means for supplying waves of a given range of frequencies to each of said channels, and transformers in said channels, certain of said transformers being in one of said channels, and certain of said transformers being in said other channel, any difference between the sum of the phase shifts of the latter' transformers and the sum of the phase shifts of said transformers in said one channel having a predetermined relation to frequency over the given frequency range, and one of said transformers in one of said chaunels having electrical constants substantially different from those of any one of said transformers in the other channel.

6. In combination, two wave transmission channels, means for supplying waves of the same frequencies to said chamiels, and transformers in said channels, certain of said transformers being in one of said channels, and cert-ain of said transformers being in said other channel, the sum of the phase shifts of the latter transformers being substantially equal to the sinn of the phase shifts of said transformers in said one channel at the frequencies of said waves, and one of said transformers in one ofsaid channels having;` electrical constants substantially different from those of any one of said tranformers in the other channel.

7. In combination, two wave transmission channels, means for supplyingr waves of the same frequencies to said channels, and transformers in said channels, certain of said transformers being in one of said chanaiid certain of said transformers different in number being' in said other channel, any difference between the sum of the phase shifts of the latter transformers and the sum of the phase shifts of said transformers in said one channel having a predetermined relation to frequency over the frequency range of said waves.

8. In combination, two wave transmission channels, means for supplying waves of the same frequencies to said channels, and trans- `formers in' said channels, certain of said transformers-being in lone ofsaid channels,

andcertain of said transformers different ink number being vin said other channel, the. sum i of the phase shifts of the latter transformers 9. I n combinatiomtwo wave paths having y portions separate and apart in common, said portions )oining said part at the same point, and transformers in said separate portions,

certain of saidftransformers being in one of i lto said portions and certain of said' transform- :ers being insaid other portion, any dierence between the sum of the phase shifts-of the `-latter-transformers and the "sum of the phase shifts o f said transformers 'in saidY one portion being substantially proportional to frequency over a frequency-range of substantial width, and one ofsaid transformers in"one of said channels having electrical consta-nts substantially diiferent from those 0f any one of saidtransformers in the other channel.

10.1n combination, two wave transmis` sion channels, means for supplying waves of the same frequencies to said channels, and

transformers in said channels, certain of said transformers'being in one of said channels,

and certain of said transformers different innumber being in saidV other channel, the sum of the phase shifts of the latter'transformers being substantially equal to the sum of thev phase shifts of said transformers in said one channel at the frequencies ofsaid waves,fand the phase shiftof each of a plurality of said transformers iii one of said channels being substantially smaller than thev phase shift of one of said transformers in the other chan-- nel.

11. In combination, two, wave transmission channels, wave receiving means for correlating effects of waves transmitted through said.' channels, certain of saidtransfoiiners being f in one of said channels, and certain of said! said channels, and transformers-yin transformers diiferent'in number being in said other channel, vthe sum"of the phase shifts of the latter transformers being sub-` stantially equal to the sum of the phase shifts of said transformers insaid one channel, at the frequencieslof said waves.

wave collecting means,`a radio receivingl circuit, twoantenna transformers connectedtd saidv Wave collecting means in tandem with each other for transmitting signals tosaid connected to said wave'eollecting means for transmitting interference compensating waves to said circuit, the phase shift of said f frequency.

tenna `transformers in tandem, at the signalV 13; A radio receiving system comprising `wave collectingV means, a radio receiving vcir- Vvcharacteristic possessing a predetermined relation Vto the frequency-phase shift characteristic of said two antenna transformers in 80 tandem, over theyfrequency, range of said signals. I c i 14, A radio receiving system comprising wave collecting means, a radio receiving circuit, two antenna. transformers connected tof185- v said wave collectingmeans'in tandem with each other for transmitting' signals to said circuit, and a compensatingtransformer connected to said wave collecting means for transmitting interference compenea-tingi90'4 waves to said circuit, said compensating transformer having a frequency-phase shift characteristic possessinga predetermined relation to the frequency-phase shift characteristie of said two antenna transformers linSMi tandem, over the frequency range of said signals, and the phase shift of each of said two antenna transformers being substantially smaller than the .phase shift of said compensating transformer. 1 00 15.A radio telephone receiving system comprising wave collecting; means, vwave y combining means, a radio telephone receiver connected to 4said combining :mea-ns, two antennatransformers connected to said wave 15105 collecting means in tandem with each other for transmitting radio telephone signals to said combining means, a compensating trans- Y former `connected, tosaid wave collecting 4means Afor transmitting Vinterference com-:5110V pensating waves to `said'combining means, any difference between the phase Vshift of said compensating transformer and the phase shift of said two antenna. transformers in `tandem having' apredetermined relation v's011115` frequency overgthe frequency range of said signals, and adjustable-phase shifting means 1- gfor equalizing the two Vphase shifts over said Y I' no' 12. A radio receiving system comprising i a he 16; In combination, two wave transmissioniilzo Vchannels'having portions separate and a portion inicomin'oma bridge transformer net---i worlrincluding a three windingtransformer, Y means connectingtwo` ofsaid windings in circuit, and a compensating transformer one of Vsaid separate fportions, and a two V125* vwinding transformer introducing in said other separate portion a phase shift equal to that introduced in said one portion .by said ,.Ynetwork., Y

1.17,; Aradio receiving system comprising; ai '5136-- plurality of wave antennae arranged substantially broadside to an interfering source, a receiving circuit, a path for each antenna for currents corresponding to signal and interfering energy received by the antenna, 1e-ans for combining the currents from these paths to produce current having signal and interfering components, a path for each antenna for currents corresponding to interfering energy received by the antenna, means for combining the currents from the last mentioned paths to produce an interfering current, means for adjusting the relative` an odd number of wave antennae arranged substantially broadside to an interfering source, a receiving circuit, a path for each antenna for currents corresponding to signal and inte 1fering energy received by the antenna, means for combining the currents from these paths to produce a current having signal and interfering components, a path for each antenna for currents corresponding to interfering` energy received by the antenna, means for combining the currents from the last mentioned paths to produce an interfering current, means for adjusting the relative phases of the combined currents sothat the interf ring current is in opposite phase to the interfering component, means for so combining the phase adjusted currents that the interfering component is neutralized, and means for transmitting the signal current from the last mentioned combining means to the receiving circuit, said paths comprising transformers and the combined phase shifts of said transformers in each path being the same for each path, certain of the transformers conjugately connecting certain of the paths.

19. In combination, two wave transmission channels, means for supplying waves of a given range of frequencies to each of said channels, and transformers in said channels, A certain of said transformers being 1n one of said channels, and certain of said transformers being in said other channel, any difference between t-he sum of the phase shifts of the latter transformers and the sum of the phase shifts of said'transformers in said one channel having a predetermined relation to frequency over the given frequency range,

and one of said transformers in one of said channels having an impedance ratio substantially different from that of any one of said transformers in the other channel.

20. In combinaton, two wave transmission channels, means for supplying waves of a given range of frequencies to each of said channels, and transformers in said channels, certain of said transformers being in one of said channels, and certain of said transformers being in said other channel, any difierence between the sum of the phase shifts of the latter transformers and the sum of the phase shifts of said transformers in said one channel having a predetermined relation to frequency over the given frequency range, and one of said transformers in one of said channels having a winding impedance different from any corresponding impedance of any one of said transformers in the other channel.

In witness whereof, I hereunto subscribe my name this 25th day of August, A. D., 1927.

HORACE IVHITTLE. 

